The present invention relates to a silver halide photographic light sensitive material.
Photographic silver halide emulsions have lately been more severely demanded than ever before to be improved on the photographic characteristics thereof; i.e., to be so improved as to have a higher sensitivity, more excellent graininess, higher sharpness, lower fog density, more adequately wide exposure scale, and the like.
For such demands, a silver iodobromide emulsion containing from zero to 10 mole% silver iodide are well-known as a high-sensitivity emulsion. And for the preparation of such high-sensitivity emulsions there have been conventionally known pH- and pAg-control methods such as the ammoniacal method, neutral method, and the like, and mixing methods such as the single-jet method, double-jet method, and the like.
In order to accomplish the still higher sensitivity, more improved graininess, higher sharpness and lower fog density on the basis of these known techniques, technical means therefor have been pursued to the utmost extent and made practical reality.
In silver iodobromide emulsions which are the subject of the present invention, researches have been conducted on emulsions wherein not only the crystal habit and granularity distribution thereof but also the silver iodide concentration distribution inside the individual silver halide grains thereof are controlled.
The most orthodox way to accomplish such photographic characteristics as the above-mentioned sensitivity, excellent graininess, high sharpness, low fog density, and the like, is to improve the quantum efficiency of the silver halide. Knowledge of solid state physics is positively introduced in for this purpose. A study in which the quantum efficiency is theoretically calculated to make considerations on the influence of the granularity distribution is described in, e.g., `Interactions Between Light and Materials` p. 91, of the prepared texts for the Tokyo Symposium 1980 for the Progress in Photography. This study predicts that the preparation of a monodisperse emulsion with its granularity distribution being narrowed will be effective in improving the quanturm efficiency. And in addition, the inference that the monodisperse emulsion is also advantageous for attaining efficiently a high sensitivity with its fog remaining low in a process called `chemical sensitization` that will be detailed hereinafter is considered reasonable.
The production of a monodisperse emulsion on an industrial scale, as is described in Japanese Patent Publication Open to Public Inspection (hereinafter referred to as Japanese Patent O.P.I. Publication) No. 48521/1979, requires the theoretically found control of the supplying rate of the silver and halogen ions to the reaction system under precise pAg and pH controls and under an adequate stirring condition of the reaction system. The silver halide grain of the emulsion produced under such conditions is in the cubic, octahedral or tetradecahederal form; that is, the emulsion comprises regular crystal grains each having (100) and (111) faces in various proportions, and such regular crystal grains are known to be highly sensitizable.
On the other hand, silver iodobromide emulsions comprising polydisperse twin grains are conventionally known as the emulsion suitable for a high-speed photographic film.
In addition, plate twin grains-containing silver iodobromide emulsions are disclosed in Japanese Patent O.P.I. Publication No. 113927/1983 and others.
On the other hand, raising the development activity, increasing the sensitivity, and the like, by the application of multistratified-type silver halide grains formed by coating a plurality of shells around the internal core are described in Japanese Patent O.P.I. Publication No. 22408/1978, Japanese Patent Examined Publication No. 13162/1968, J. Photo. Sci., 24, 198 (1976), and the like.
The silver halide grain provided with coat stratums by the halogen substitution as the outermost stratum thereof is described in West German Pat. No. 2932650, Japanese Patent O.P.I. Publication Nos. 2417/1976, 17436/1976, 11927/1977, and the like. However, such silver halide grains are not practically applicable as the grains for a negative emulsion in respect that they, although capable of accelerating the fixing rate, restrain the development to the contrary, thus being unable to provide any adequate sensitivity.
And positive-type (internal latent image-type) silver halide grains each having outside the core thereof a plurality of coat stratums by the halogen substitution are known and detailed in U.S. Pat. Nos. 2,592,250 and 4,075,020, Japanese Patent O.P.I. Publication No. 127549/1980, and the like. Such silver halide grains are those frequently used in the internal latent image-type direct positive light-sensitive material for use in the diffusion transfer process and are by no means applicable to any one or ordinary negative-type emulsions because the internal sensitivity thereof is excessively high.
Meanwhile, Japanese Patent O.P.I. Publication Nos. 181037/1983, 35726/1985, 116647/1984, and the like, also disclose those silver halide grains each having shell stratums around the internal core thereof, the shell stratums each containing a diverse amount of iodide.
In the silver halide photographic light-sensitive material's field, color light-sensitive materials whose sensitivity exceeds an ISO speed index of 1000 have in recent years made their appearance thanks to the remarkable progress in various techniques. However, it is the status quo that such light-sensitive materials, since they become, without exception, deteriorated in the sharpness as well as in the graininess as their sensitivity goes up, produce images inferior in quality to those from conventional light-sensitive materials, thus being unsatisfactory for the appreciation by consumers. Upon this, great hope has now been placed on the realization of high-speed light-sensitive materials excellent in the sharpness as well as in the graininess.
In the astrophotography, indoor photography or sports photography, still higher-speed negative-type light-sensitive materials are indispensable.
A color image is usually obtained as a result of the formation of a dye image by the coupling reaction of couplers with the oxidized product of a color developing agent. In a multicolor photographic element, the subtractive method is usually used for the color image formation, and the dyes to be formed by the coupling may be normally the cyan, magenta and yellow dyes which are formed in the respective silver halide emulsion layers or other layers adjacent thereto, the emulsion layers being sensitive to the wavelength regions the rays of which are absorbed by the image dyes; i.e., sensitive to the red, green and blue regions of the spectrum.
Those couplers forming these dyes are desirable to be such that the color dye produced therefrom be very sharp in its hue; be excellent in the color reproducibility; cause no such discoloration as reduction discoloration; and be excellent in the produced dye cloud's graininess.
Those phenols and naphthols conventionally used as the cyan coupler to be contained in a silver halide emulsion having the sensitivity thereof in the red region of the spectrum are couplers excellent in the color reproducibility because the absorption maximum (.lambda.max) of the color-formed dye therefrom is generally in a longer wavelength region and the sub-absorption thereof in the green region is small. These couplers, however, have the disadvantages that the dye formed therefrom is generally discolored in a weak-oxidation bleach-fix process to form a leuco dye, thus causing a failure in the color formation.
In order to solve such the disadvantage, the use of a cyan coupler not causing any reduction discoloration in the bleach or bleach-fix process is required, and as the cyan coupler of this type, e.g., British Pat. No. 1,011,940, U.S. Pat. Nos. 3,446,622, 3,996,253, 3,758,308, 3,880,661, and the like, disclose those phenol-type cyan couplers having an ureido group in the second position thereof. However, these couplers are unfavorable in respect of the color reproducibility because the absorption spectrum of each of the dyes formed therefrom has a sub-absorption in a shorter-wavelength region.
On the other hand, those ureido-phenol-type cyan couplers having a specific ureido group in the second position of the phenol and an acylamino group in the fourth position of the phenol, which are described in Japanese Patent O.P.I. Publication No. 65134/1981, are known as the coupler improved so that the cyan dye formed therefrom is not discolored and the cyan dye's absorption maximum in the spectrum is in a relatively longer wavelength region. However, it has now been found as a result of our investigation that the use of such ureido-type cyan couplers causes outstanding deterioration of the sensitivity as well as of the graininess of film where the film has been allowed to stand over a long period of time, particularly, under high temperature/high humidity conditions.